The present invention relates generally to processes for producing a cast resin coils,and more particulary to a cast resin coil that consists of a plurality of flat coils superimposed axially on each other, and a cast resin coil thus produced.
German Utility Model 71 26 814 discloses a winding for a transformer which consists of axially superimposed individually wound flat coils. The individual flat coils have intervening spaces between their inner and outer partial windings which lie coaxially one within the other. The partial windings can be wound continuously from the same conductors. The intervening spaces of the corresponding flat coils form, in this connection, axial cooling channels. The winding can be encapsulated in casting resin. It has been found in practice that the encapsulating of the flat coils is very problematical. No solution for this problem is indicated in the German Utility Model.
Up to the present time, therefore, an inner cast resin coil and an outer cast resin coil were produced separately, then placed coaxially one within the other and mechanically connected to each other so that a concentric cooling channel was present between the two cast resin coils.
From U.S. Pat. No. 4,129,938 a process is known for producing an encapsulated winding of wire conductor having cooling channels. For this purpose, after a predetermined number of inner windings, an impregnable non-woven fabric is first of all placed on the winding. Thereupon, moldings which form cooling channels are placed on and an additional layer of the impregnable non-woven fabric is placed over this. An outer partial winding is then applied. The entire winding is encapsulated, the moldings being removed after the encapsulation. Axial cooling channels which are distributed uniformly over the circumference are then produced in the winding. This known winding technique, however, cannot be used in an arrangement consisting of a plurality of flat coils, since the moldings used in the individual flat coils were difficult to remove. Furthermore, the alignment of the intervening spaces of the individual flat coils with respect to each other is difficult.
From British 936 380, there is known the use of a non-woven fabric and of moldings for the forming of cooling channels for transformer coils.
The exact development of the coil, particularly in the transfer region of the coaxially arranged individual coils, is not taken up in any of the documents mentioned.
The present invention is directed to the problem of developing an improved process for producing windings that have cooling channels and are built of several flat coils. The present invention is also directed to the problem of developing an improved cast resin coil with strip conductors.